Method of making synthetic straw



Patented Aug. 11, 1936 UNITED STATES PATENT OFFICE Whitehead,

Cumberland,

Md., assignors to Celanese Corporation of America, a corporation of Delaware No Drawing. Application April 27, 1931, Serial No. 533,360

Claims.

This invention relates to the manufacture of synthetic straw and the like made of or containing organic derivatives of cellulose and is directed more specifically to the production of straw- 5 like material that is more versatile in its use than straws heretofore produced.

An object of our invention is to produce artificial or synthetic straw having a more or less permanent twist imparted thereto. A further object of our invention is to produce artificial straw comprising a plurality of ends of finer straw-like material, Other objects of this invention will appear from the following detailed description.

In our co-pending U. S. application Serial No.

- 361,832 filed May 9, 1928, of which this is a continuation in part, we have described the process of producing artificial straw by treating yarns of organic derivatives of cellulose with a solvent and then causing the same to coalesce by applying heat and pressure thereto.

We have now found that the synthetic straw, produced in accordance with said application or in any other manner, may be treated so as to obtain a product that has many uses to which ordinary fiat straw is not applicable. Thus by twisting such straw, preferably while it contains a smallamount of residual solvent, a twisted straw may be obtained which has a relatively permanent twist. Moreover by twisting such straw at 30 a high rate, or by subjecting the same to sudden and severe bending, the straw may be split into a plurality of fine straws having a denier corresponding to that of the yarns originally employed in coalescing, which individual fine straws may 35 or may not be twisted together.

In one aspect of our invention we impart a more or less permanent twist to synthetic straw made in any manner and containing organic derivatives of cellulose so as to render it more suit- 40 able for various uses. In another aspect of our invention, we sharply twist or bend artificial or synthetic straw which has been made by coalescing and flattening a plurality of ends of yarns each consisting of a plurality of individual filaments, by application of a solvent and heat and pressure, so that there is produced a number of finer straws associated together with or without twist.

The straw that is twisted and/or sharply bent 50 so as to be twisted and/or split into a plurality of finer filaments may be made in any suitable manner, although we prefer to treat the straw made generally in accordance with the method described in our U. S. application Serial No.

361,832 filed May 9, 1928.

The material to be coalesced and containing the thermoplastic derivative of cellulose may be in the form of fine filaments, of say 2 to 25 denier, which filaments may be twisted in the form of a .yarn or which may be untwisted. 5 These filaments may be in the form of artificial bristles of say 50 to 1000 denier or more or they may be in the form of artificial straw.

The thermoplastic derivative of cellulose employed in the material to be treated in accord- 10 ance with our invention is preferably an organic derivative of cellulose, examples of which are organic esters of cellulose and cellulose ethers. Examples of organic esters of cellulose are cellulose acetate, cellulose formate, cellulose propionate and cellulose butyrate, while examples of cellulose ethers are ethyl cellulose, methyl cellulose and benzyl cellulose.

If particular ornamental effects are desired, such as are produced by. differential color ef- 2O facts or by differential lustre, yarns of non-thermoplastic material may be associated with the thermoplastic material prior to coalescing to form the artificial straw. Examples of such yarns are those made of natural silk, cotton, reconstituted 25 cellulose, wool, etc. Often the presence of these non-thermoplastic materials improves the physical strength and knotting properties of the final straw produced. If metallized effects are desired, fine fiat metal bands, such as are used in making tinsel, or metallized threads or yarns may be associated with the filaments of the thermoplastic material prior to coalescing. If desired a bronze or aluminum powder or other effect materials may be incorporated in the prodnot at any suitable stage of manufacture to produce metallic or other eifects.

The filaments or yarns or other materials to be coalesced may be drawn from bobbins or other suitable packages to be treated by our process, or they may be drawn directly from the spinning machine where they are produced.

The coalescing liquid applied to the associated yarns, filaments and the like containing an organic derivative of cellulose prior to subjecting the same to heat and pressure contains a substance which is either a solvent or a restricted solvent for the organic derivative of cellulose. Examples of such solvents or solvent mixtures are acetone, ethylene dichloride and ethyl or methyl alcohol, dischlorethylene .and ethyl or methyl alcohol, etc. Often it is advantageous to add high boiling solvents or plasticizers such as triacetin, diacetin, dibutyl tartrate, tricresyl phosphate to the coalescing fluid. If desired, this solvent liquid may have dissolved therein a suitable desired proportion of an organic derivative of cellulose, and this organic derivative of cellulose may be any of those above mentioned. The solvent liquid may be applied in any suitable manner thus by means of wicks, rolls, rods, by spraying the same onto the yarns or filaments, or by immersing the same in the liquid in their passage to the heat and pressure device. If the straw is to be split into finer straws, a relatively smaller amount of solvent or restricted solvent is applied.

Any suitable means may be employed for applying heat and pressure to the yarns or filaments of organic derivatives of cellulose after the solvent liquid has been applied thereto. This pressure device may assume the form of a pair of rollers rotating at opposite directions at the same peripheral speed. At least one of the rollers is heated to a suitable temperature by any suitable means such as steam, hot water, electrical resistances, etc. These rollers may have plain and smooth surfaces, or they may have interrupted surfaces. Thus they may be engraved, fluted or have other surfaces to crinkle, emboss or produce similar fancy effects upon the finished artificial straw. One of the rolls may be constructed and operated as a printing roll and be caused to apply a suitable printing paste to the artificial straws under formation, and thus produce a printed design on the product.

As to temperature and pressure to be employed in coalescing, the application of high pressures and/or high temperatures produces a clear continuous product and these are preferably used when the straw is to be merely tinted without being split. Lower temperatures and/or pressures iay be employed to obtain products where the outline of the original filaments, yarns and the like are still perceptible, and these are preferably employed when the straw is to be split.

The amount of solvent applied will vary with the heat applied and also the size of the yarn and the size of the filaments in the yarn. Generally,

- the finer yarns and finer filaments require less solvent to effect coalescence.

Another mode of producing the straw to be treated in accordance with this invention is to moisten the yarns with a coalescing solvent and then draw the same under slight tension through a tortuous path between two or more knife-edge members, which have the effect of spreading out the wetted band into a flat straw.

The synthetic straw may be twisted in accordance with this invention by any suitable method, such as by means of ring, fiier, cap spinning bobbins or the like. If this twisting is done at a relatively low rate, and particularly when the synthetic straw contains a small amount of residual solvent, a more or less permanent twist is imparted thereto, and the original straw may or may not be split up into finer straws. However by twisting such straw, particularly when made by coalescing of a plurality of ends of yarn, at comparatively high rates, such as with twisting spindles rotating at 5000 R. P. M., the straw is twisted and at the same time split into finer straws, the individual size of which is approximately equal in denier to that of the individual ends of yarn used in the coalescing process.

However it is not necessary that the straws be twisted to obtain the splitting effect. Any process involving sudden and severe bending or twisting backwards and forwards of the straw effects the splitting of the straw into finer straws. Thus the straw may be passed through a fine slot and then immediately through another slot at right angles to the first slot, thus causing the straw to twist suddenly at right angles. This effects the splitting of the straw into finer straws.

We have found it advantageous to effect the twisting or other splitting process while the straw contains a small amount of residual solvent from the coalescing process or other process used for making the same, since when traces of the solvent are present, not only does cleaner splitting of the straw occur, but where twisting is involved, the loss of solvent during twisting process or after the process sets the new form of straw in its twist. However the twisting or processing of the yarn while it contains no residual solvent is within the scope of this invention.

If desired, the twisting or other splitting process may be done continuously with the coalescing process, although it is preferable to dry the straw so as to drive olf the residual solvent substantially before twisting or subjecting to severe bending. This drying may be effected by passing the straw after it leaves the coalescing rollers through a long drying path of say 8 meters at a speed of say 40 meters per minute or passing the straw in contact with drying cans or drums rotating at substantially the same peripheral speed as the coalescing rolls.

It will be understood that when the coalescing process is employed, the individual filaments forming the yarn coalesce together to form fiat bands, and that these individual bands or strips formed by the coalescence of the filaments of the yarn generally do not split during the process.

Where color effects on the films or artificial straws are desired, suitable dyestuffs may be applied at any suitable stage of the process of manufacture; that is, prior to the application of the solvent liquid, simultaneously therewith or after the same has coalesced to form the finished product. Where the dyestuff is applied prior or subsequent to application of the coalescing solvent, it is preferably in the form of a solution of the dyestuff in organic solvents, as described in the application of W. Whitehead, Serial No. 284,673, filed April 4, 1928. When the dyestuff is applied prior to the application of the coalescing liquid, the same may be applied by means of wicks, rolls and the like in a continuous manner to produce uniform color, or intermittently to form differential color effects. The dyestuff may be applied if desired on one or more of the pressure rolls. A convenient mode of application of the dye is in solution in the coalescing solvent. Other modes of applying the dyestufi may be used. Thus the finished straw may be dyed in hanks or in the form of other packages by any suitable known dyeing methods.

Artificial straw or film that has a suitable lustre, or which is opaque, may be produced in accordance with our invention, and this delustered or opaque effect may be obtained as a continuous effect or only intermittently as desired. This delustered or opaque effect may be produced by subjecting the film or artificial straw to the action of water or other aqueous media, alcohol, steam or other delustering agency, after it has been formed by coalesence under the action of the solvent under heat and pressure. If a liquid is employed as the coalescing agent which consists of a mixture of a solvent for the organic derivatives of cellulose and a less volatile nonsolvent for the same in suitable proportions, upon evaporation of the solvent for the organic derivative of cellulose, the residual nonsolvent liquid causes delustering of the resulting straw. Another mode of obtaining this effect is to apply a soluble metal salt (such as that of barium, strontium or calcium) to the yarns or filaments about to be coalesced, either by the coalescing liquid or by separate application, and then subsequent to the coalescing step subjecting the straw or film thus produced to a chemical treating bath that precipitates the metal in the form of an insoluble compound (such as sulphate, carbonate or phosphate).

If high lustre and water proof properties are desired in the final straw, such straw after coalescence or during coalescence may be pressed between smooth rollers having waxes like carnauba wax or beeswax thereon.

In order further to illustrate our invention but without being limited thereto, the following specific example is given.

Example A number of ends of yarn, say 15, made of cellulose acetate that is soluble in acetone, and each yarn having a denier of 300 and containing 80 filaments, is employed. These individual ends of yarn may have a twist of say 2 turns per inch. These yarns may be wound from bobbins or may be drawn directly from the spinning machine from which they are formed, or some of the yarn may be drawn from bobbins and others from spinning machines. These yarns are passed in contact with a slowly rotating fiannel roll which dips in a bath of acetone to a pair of coalescing rolls heated at 75 C. and rotating with a peripheral speed of 40 meters per minute. The flannel roll is caused to rotate at such speed that the amount of acetone applied to the yarn is equal to of the weight thereof. The top roll is caused to press on the straw being formed with a pressure of 10 pounds per square inch.

The straws so formed which may have a width of say 0.25" and a thickness of say 0006" are then wound up on a bobbin. While the straw still contains not less than 0.1% residual solvent, the bobbin of straw so formed is placed on vertical spindles rotating at 8000 R. P. M., the straw is drawn over the head of the bobbin through a guide situated conveniently at a short distance above the centre of the bobbin, and from thence to a winding up bobbin driven in a conventional manner. The winding up bobbin is caused to rotate at a suitable speed, say 25 M. P. M., according to the amount of twist required. The product obtained by this processing consists of a twisted association of 15 ends of fine straw of 300 denier each, each having a width of 1/60 of an inch and a thickness of 0.006.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. Method of treating synthetic straw and the like produced by coalescing a plurality of yarns or filaments, which comprises subjecting the straw or the like to severe bending so that the material is split lengthwise and forms a plurality of finer straws.

2. Method of treating synthetic straw and the like produced by coalescing a plurality of yarns or filaments containing cellulose acetate, which comprises subjecting the straw or the like to severe bending so that the material is split lengthwise and forms a plurality of finer straws.

3. Method of treating synthetic straw and the like produced by coalescing a plurality of yarns or filaments, which comprises bending the straw or the like in such a manner as to split the same to form a plurality of finer straws and to leave said finer straws substantially free from twist.

4. Method of treating synthetic straw and the like produced by coalescing a plurality of yarns or filaments containing cellulose acetate, which comprises bending the straw or the like in such a manner as to split the same to form a plurality of finer straws and to leave said finer straws substantially free from twist.

5. Method of preparing an association of fine straw-like products, which comprises subjecting a synthetic straw produced by coalescing a plurality of yarns or filaments containing an organic derivative of cellulose to an operation involving a sharp and severe change of direction of one portion thereof with respect to an adjacent portion, whereby the synthetic straw is split into finer straw-like products.

6. Method of preparing an association of fine straw-like products, which comprises a synthetic straw produced by coalescing a plurality of yarns or filaments containing cellulose acetate to an operation involving a sharp and severe change of direction of one portion thereof with respect to an adjacent portion, whereby the synthetic straw is split into finer straw-like products.

7. Method of preparing an association of fine straw-like products, which comprises subjecting a synthetic straw produced by coalescing a plurality of yarns or filaments containing cellulose acetate while it contains a small amount of solvent to an operation involving a sharp and severe change of direction of one portion thereof with respect to an adjacent portion, whereby the synthetic straw is split into finer straw-like products.

8. Method of preparing an association of fine straw-like products, comprising coalescing a plurality of yarns containing an organic derivative of cellulose by heat and pressure in the presence of a solvent to form a straw-like product, and

then splitting the resulting product into a plurality of finer straw-like material.

9. Method of preparing an association of fine straw-like products, comprising coalescing a plurality of yarns containing cellulose acetate by heat and pressure in the presence of a solvent to form a straw-like product, and then splitting the resulting product into a plurality of finer straw-like material.

10. Method of preparing an association of fine straw-like products, comprising coalescing a plurality of yarns containing cellulose acetate by heat and pressure in the presence of a solvent to form a straw-like product and then subjecting the resulting product to a twisting operation while it contains residual solvent and then subjecting the resulting product to a severe twisting operation whereby the same splits into a plurality of finer straw-like materials which are twisted together.

CAMILLE DREYFUS. WILLIAM WHITEHEAD. 

